The term “wireless access terminal” as used herein is intended to refer to wireless communication devices used to access a wireless communication system, such as a wireless Wide Area Network (WAN), wireless Metropolitan Area Network (MAN), wireless Local Area Network (LAN), wireless Personal Area Network (PAN), or the like. For example, the term “wireless access terminal” as used herein can be used to refer to a device with cellular telephone type capabilities, e.g., a device that can be used to access a cellular telephone type network. It will be understood that today's wireless access terminal are capable of operating over a variety of network types, using a variety of technologies.
For example, today's cellular telephone is typically capable of operating in a traditional cellular network or a Personal Communication Service (PCS) network. As new capabilities are introduced, the line between different devices, and the network types they operate over, is becoming more blurred so that conventional devices can operate over wireless MANs, WANs, LANs, etc., to communicate voice and/or data information using third and fourth generation technologies. The very idea of a wireless communication device has evolved as wireless communication capabilities have been incorporated into laptop computers, Personal Digital Assistants (PDAs), digital music players, etc. Accordingly, the term “wireless access terminal” as used herein is intended to refer to all such devices.
As mentioned, a wireless access terminal often must be able to communicate using a variety of technologies. When a wireless access terminal initially accesses the network over which it is to operate, it must go through an acquisition and initialization process during which it acquires the network and obtains all of the information necessary to communicate using the network. This process typically involves the wireless access terminal scanning the wireless spectrum to acquire one or more pilot channels that identify network base stations. Once the wireless access terminal has acquired a pilot channel, it can then, e.g., acquire various control channels over which it can obtain information needed to communicate with the base station, paging channels over which it can obtain messages from the base station, and traffic channels over which it can communicate. A wireless access terminal uses various protocols and routines to perform such tasks.
If the wireless access terminal is configured to operate over more than one network using more than one technology, then it must go through this, or a similar process for each network. If the terminal is currently communicating over a first network, then to communicate over a second it must suspend communication with the first network and initialize with the second network. But first, the terminal must determine if the second network is available. In conventional terminals, if the terminal switches to monitor for the presence of a second network, the terminal's protocols, including the layer 2, layer 3, and modem control protocols, enter a freeze state where it temporarily stops decoding and receiving data over the first network. This process is referred to as the “tune away.”
During tune away, the terminal protocols associated with the first network are often deactivated. When the modem switches back, i.e., “tunes back,” then the terminal must go through the entire initialization process again. This process wastes resources, and since most conventional terminals that work over multiple networks are configured to periodically tune away to check for other networks, the resources are wasted periodically and continuously while the terminal is activated. The cumulative effect is increased power consumption and inefficiencies, which lead to reduced performance and reduced battery lifetimes. Battery lifetime, always important, is becoming even more important because today's terminals have increased functionality. Increased functionality means increased power consumption, which reduces battery lifetime. Therefore, the inefficiencies of the conventional tune away-tune back process can have a significant effect.